One document matched: draft-aboba-pppext-eap-iana-02.txt
Differences from draft-aboba-pppext-eap-iana-01.txt
PPPEXT Working Group B. Aboba
INTERNET-DRAFT Microsoft
Category: Standards Track
<draft-aboba-pppext-eap-iana-02.txt>
12 October 2002
Updates: RFC 2284
EAP IANA Considerations
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC 2026.
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Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This document describes the IANA considerations for Extensible
Authentication Protocol (EAP).
This document updates RFC 2284.
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1. Introduction
This document provides guidance to the Internet Assigned Numbers
Authority (IANA) regarding registration of values related to the
Extensible Authentication Protocol (EAP),defined in [RFC2284], in
accordance with BCP 26, [RFC2434].
1.1. Specification of Requirements
In this document, several words are used to signify the requirements of
the specification. These words are often capitalized. The key words
"MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD
NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in [RFC2119].
1.2. Terminology
The following terms are used here with the meanings defined in BCP 26:
"name space", "assigned value", "registration".
The following policies are used here with the meanings defined in BCP
26: "Private Use", "First Come First Served", "Expert Review",
"Specification Required", "IETF Consensus", "Standards Action".
2. IANA Considerations
There are two name spaces in EAP that require registration: Packet Codes
and Method Types.
EAP is not intended as a general-purpose protocol, and allocations
SHOULD NOT be made for purposes unrelated to authentication.
2.1. Recommended Registration Policies
For registration requests where a Designated Expert should be consulted,
the responsible IESG area director should appoint the Designated Expert.
For Designated Expert with Specification Required, the request is posted
to the EAP WG mailing list (or, if it has been disbanded, a successor
designated by the Area Director) for comment and review, and MUST
include a pointer to a public specification. Before a period of 30 days
has passed, the Designated Expert will either approve or deny the
registration request and publish a notice of the decision to the EAP WG
mailing list or its sucessor. In making the decision, the Designated
Expert will take into account the security guidelines described in
Section 4. A denial notice must be justified by an explanation and, in
the cases where it is possible, concrete suggestions on how the request
can be modified so as to become acceptable.
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Packet Codes have a range from 1 to 255, of which 1-4 have been
allocated. Because a new Packet Code has considerable impact on
interoperability, a new Packet Code requires Standards Action, and
should be allocated starting at 5.
The original EAP Method Type space has a range from 1 to 255, and is the
scarcest resource in EAP, and thus must be allocated with care. Method
Types 1-36 have been allocated, with 20 available for re-use. Method
Types 37-191 may be allocated following Designated Expert, with
Specification Required. Release of blocks of Method Types (more than 1
at a time for a given purpose) should require IETF Consensus. EAP Type
Values 192-254 are reserved and allocation requires Standards Action.
Method Type 255 is allocated for Vendor-Specific extensions as described
in Section 3, and the use of that should be encouraged instead of
allocation from the original global Method Type space, for functions
specific only to one vendor's implementation of EAP, where no
interoperability is deemed useful.
When used with a Vendor-Id of zero, Method Type 255 can also be used to
provide for an expanded Method Type space. Expanded Method Type values
256-4294967295 may be allocated after Type values 1-191 have been
allocated, using Designated Expert with Specification Required.
3. Vendor-specific
Description
Due to EAP's popularity, the original Method Type space, which only
provides for 255 values, is being allocated at a pace, which if
continued, would result in exhaustion within a few years. Since many
of the existing uses of EAP are vendor-specific, the Vendor-Specific
Method Type is available to allow vendors to support their own
extended Types not suitable for general usage. The Vendor-specific
Type may also be used to expand the global Method Type space beyond
the original 255 values.
Peers not equipped to interpret the Vendor-specific Type, or who
support the Vendor-Specific Type, but find the proposed Vendor-Id to
be unacceptable, MUST send a Nak, and negotiate a more suitable
authentication method.
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A summary of the Vendor-specific Type format is shown below. The
fields are transmitted from left to right.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Vendor-Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| String...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
255 for Vendor-specific
Vendor-Id
The Vendor-Id is 3 octets and represents the SMI Network Management
Private Enterprise Code of the Vendor in network byte order, as
allocated by IANA. A Vendor-Id of zero is reserved for use by the
IETF in providing an expanded global EAP Type space.
String
The String field is one or more octets. The actual format of the
information is site or application specific, and a robust
implementation SHOULD support the field as undistinguished octets.
The codification of the range of allowed usage of this field is
outside the scope of this specification.
It SHOULD be encoded as follows. The Vendor-Specific field is
dependent on the vendor's definition of that attribute. An example
encoding of the Vendor-Specific attribute using this method follows.
Example Implementation
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Vendor-Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-Specific...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Vendor-Type
The Vendor-Type field is four octets and represents the vendor-
specific Method Type. Where a Vendor-Id of zero is present, the
Vendor-Type field provides an expanded global EAP Type space,
beginning with EAP Type values of 256.
Vendor-Specific
The Vendor-Specific field is dependent on the vendor's definition of
that attribute. Where a Vendor-Id of zero is present, the Vendor-
Specific field will be used for transporting the contents of EAP
Methods of Types 256 or greater.
4. Security Considerations
EAP was designed for use with dialup PPP [RFC1661] and wired [IEEE802]
networks such as Ethernet [IEEE8023]. On these networks, an attacker
would need to gain physical access to the telephone or switch
infrastructure in order to mount an attack. While such attacks have been
documented, such as in [DECEPTION], they are assumed to be rare.
However, subsequently EAP has been proposed for use on wireless
networks, and over the Internet, where physical security cannot be
assumed. On such networks, the security vulnerabilities are greater, as
are the requirements for EAP security.
This section documents the threats that exist on physically insecure
networks carrying EAP, as well as laying out the security analysis
required of an EAP method requesting a Type allocation.
4.1. Threat model
On physically insecure networks, it is possible for an attacker to gain
access to the physical medium. This enables a range of attacks,
including the following:
[1] An adversary may try to discover user identities by snooping data
packets.
[2] An adversary may try to modify or spoof EAP packets.
[3] An adversary may launch denial of service attacks by terminating
EAP conversations.
[4] An adversary might attempt to recover the passphrase by mounting an
offline dictionary attack.
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[5] An adversary may attempt to convince the Peer to connect to an
untrusted network.
[6] An adversary may attempt to disrupt the EAP negotiation in order to
weaken the authentication, gain access to user passwords or remove
confidentiality protection.
[7] An adversary may attempt to mount a denial of service attack by
modify
[8] An attacker may attempt to take advantage of weak key derivation
techniques used within EAP methods.
[9] An attacker may attempt to take advantage of weak ciphersuites
subsequently used after the EAP conversation is complete.
Where EAP is used over wireless networks, an attacker needs to be within
the coverage area of the wireless medium in order to carry out these
attacks. However, where EAP is used over the Internet, no such
restrictions apply.
4.2. Security requirements
In order to address the threats that exist where EAP is used on a
physically insecure medium, the following requirements are imposed:
[1] Mutual authentication. Mutual authentication of the communication
endpoints MUST be provided in order to protect against rogue
Authenticators.
[2] Protected conversation. On a physically insecure network, EAP
messages SHOULD be integrity and replay protected, authenticated
and confidential so as to protect against downgrade attacks,
snooping of identities, and spoofing of packets. This includes
protection of packets of types Identity, Nak and Notification, as
well as packets sent within the EAP method itself, and success and
failure indications. Where EAP is used for ciphersuite or
capabilities negotiation, these messages SHOULD be integrity and
replay protected, authenticated and confidential.
[3] Key derivation. EAP methods used on physically insecure networks
MAY derive keys in order to enable per-packet authentication,
integrity and replay protection as well as confidentiality. Where
EAP methods derive keys, the distributed keys SHOULD be master
session keys, used only for further key derivation, independent of
the ciphersuite. This eliminates the need for an EAP method to
understand how to derive keys for every ciphersuite. Rather than
inventing new key derivation techniques, well analyzed algorithms
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SHOULD be used.
[4] Dictionary attack resistance. Where EAP is used on physically
insecure networks resistance against dictionary attack SHOULD be
provided. Where password authentication is used, users are
notoriously prone to selection of poor passwords. Without
dictionary attack protection, it is easy for an attacker snooping
authentication traffic to gather a large number of authentication
exchanges, and successfully obtain a substantial fraction of the
passwords used in those exchanges via a dictionary attack. Given
the steadily declining prices of computing power, successful
dictionary attacks can now be mounted at minimal expense.
[5] Support for fast reconnect. On physically insecure media such as
wireless, it is often desirable to improve scalability and minimize
connectivity interruptions due to authentication. Where this is
desired, EAP methods MAY support "fast reconnect". After an initial
authentication conversation, this enables subsequent authentication
conversations to take place in shortened form.
[6] Acknowledged success and failure indications. Where EAP is used
over an unreliable medium, it is possible for packets to be lost.
This can result in the Peer and Authenticator having a different
interpretation of the state of the authentication conversation. As
a result, where EAP is used over an unreliable medium, EAP methods
SHOULD support acknowledged success and failure indications.
Since proposed EAP methods may be used on physically insecure methods,
it is necessary to be able to evaluate methods against the above
requirements in order to determine their suitability. In order to be
suitable for allocation of a Type code, EAP method specifications MUST
include the following:
[a] Statement of intended use. This includes a statement of whether the
method is intended for use over a physically secure or insecure
network, as well as a statement of the applicable media.
[b] Indication of security claims. This includes a statement of the
claimed security properties of the method. In particular, the
specification MUST include a vulnerability analysis and an
indication of whether the method claims to satisfy the requirements
for use on physically insecure media.
[c] Description of key hierarchy. EAP methods deriving keys MUST
describe how keys for authentication/integrity, encryption and IVs
are to be derived from the provided keying material, or a reference
to other documents providing such a description.
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[d] Indication of vulnerabilities. If the method is intended for use on
a physically insecure network, yet does not satisfy the above
requirements, the specification MUST indicate which requirements
are not satisfied, and discuss the security implications.
5. Normative references
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[RFC2434] Alvestrand, H. and Narten, T., "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC2284] Blunk, L., Vollbrecht, J., "PPP Extensible Authentication
Protocol (EAP)", RFC 2284, March 1998.
Acknowledgments
Thanks to Glen Zorn of Cisco, and Ashwin Palekar of Microsoft for
discussions relating to this document.
Authors' Addresses
Bernard Aboba
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
EMail: bernarda@microsoft.com
Phone: +1 425 706 6605
Fax: +1 425 936 7329
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Expiration Date
This memo is filed as <draft-aboba-pppext-eap-iana-02.txt>, and
expires April 19, 2003.
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